Fiber-coupled receivers are commonly employed to detect two-dimensional images. A fiber-coupled receiver generally includes a plurality of bundled optical fibers of equal length extending between opposed first and second ends. The first ends of the optical fibers are typically tightly packaged to receive the image information in parallel. In this regard, each optical fiber defines one pixel of the resulting image.
The fiber-coupled receiver also typically includes a lens for focusing the image upon the first ends of the optical fibers. While fiber-coupled receivers can detect two-dimensional images, fiber-coupled receivers can also be utilized to detect three-dimensional images. In this regard, the image information from a pulse-illuminated object would be received by the first ends of the optical fiber at slightly different times. As known to those skilled in the art, the initial signals that arrive at the first ends of the optical fibers will represent those portions of the object that is being imaged that are closest to the receiver, while signals that are received at progressively later times represent those portions of the object that are increasingly further from the receiver. By analyzing the times at which the signals are received by the first ends of the optical fibers, a three-dimensional image of the object can be reconstructed.
Conventional fiber-coupled receivers also include a detector having a plurality of array elements, one of which is generally associated with each optical fiber. In particular, each array element is generally positioned to receive the signals emitted by the second end of a respective optical fiber. Since each of the optical fibers has an equal length, the array elements receive and process the signals in parallel. In addition to detecting the signals provided by the second ends of the optical fibers, the detector generally amplifies the detected signals prior to further processing of the signals. As such, a typical detector can comprise a photo-multiplier tube having a plurality of anodes, each of which both detects and amplifies the signals emitted by the second end of a respective optical fiber.
A conventional fiber-coupled receiver also generally includes a digitizer for receiving the amplified signals from the detector and for creating a digital representation of the signals. In addition, a conventional fiber-coupled receiver typically includes a signal processor for receiving the digitized representations of the signals and for reconstructing the image. In this regard, each optical fiber corresponds to a respective pixel of the resulting image with the position of the pixel based upon the position of the first end of the respective optical fibers relative to the first ends of the other optical fibers. For a receiver designed to detect three-dimensional images, the signal processor will also analyze the differences in time at which the signals were received by the receiver, as described above.
While conventional fiber-coupled receivers can effectively detect two- and three-dimensional images, conventional fiber-coupled receivers are quite expensive and surprisingly heavy. In this regard, the requirement that conventional fiber-coupled receivers include a detector, a signal amplifier and a signal processor associated with each optical fiber significantly increases the overall cost of the receiver. As such, conventional fiber-coupled receivers may not be employed in cost-sensitive or weight-constrained imaging applications in view of their substantial costs and weight penalty.